The present invention is directed to a metal-gas battery with a cathode comprising nitrogen oxides as an active material wherein the cathode active material may be supplied in the form of an exhaust stream from a combustion process.
In prior U.S. application Ser. No. 14/150,168, a metal-nitric oxide battery was described. The metal-nitric oxide battery is of great interest due to properties such as 1) a high redox potential at 1.0 V. vs. Ag/Ag+; 2) high reversibility; and 3) negligible influence of the supporting electrolyte salt on the NO redox reaction in comparison to a metal-O2 gas battery.
A charge-discharge profile of a Li/NO gas battery was generated by using a model cell. The model battery worked well to verify the concept of this type of battery. However, the model battery employed to demonstrate the concept design displayed very low coulombic efficiency of the charge-discharge capacity, which was observed to be around 33%. Without being constrained by theory, the inventors believe that the reason for low efficiency may be the simultaneous reduction of the charged species (NO+) at a counter electrode (anode).
Under theoretical conditions, NO is oxidized on a working electrode (cathode) during charging to form a NO ion. Then, the charged species is reduced on the working electrode during discharging to return NO. However, in the model cell previously described, NO as the charged state may easily diffuse in the electrolyte media to the anode where it would be reduced back to NO even during charging. As a result of this migration and reduction, the concentration of charged species near the working electrode just after charging is significantly depleted and therefore, upon discharge the concentration of the NO is quite low in comparison to the charge capacity, and thus the coulombic efficiency is also very low.
Therefore, there is a need to improve the discharge capacity of the metal-NO cell if the system is to be commercially viable.